Is it Necessary to Replace Roof Flashings When Replacing Shingles?

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Installing new shingles is a major investment for most homeowners, so it makes good sense to take steps to protect the integrity of the roof for as long as possible. Flashing serves a single purpose: to prevent water from entering roof penetrations. Since flashing is relatively inexpensive, in the majority of cases it pays to replace it. While there are a couple of exceptions, plan to update the roof flashing for the best results.

Drip Edge Flashing

Drip edge flashing comes in two types: one to protect the bottom, or gutter edge, and the other to protect the side or roof rake edge. Both types of drip edge direct water off and away from the roof and the fascia. Drip edge comes in 10-foot strips and attaches to the roof deck before the roofing felt goes on. Unless the old drip edge is in like-new condition, replace it.

Decorative Guttering

The only time you might not want to replace gutter flashing is when you don’t want to remove decorative guttering that attaches with spikes or screws through the existing drip edge. If this is the case, you can overlay the existing drip edge with new gutter apron and cut the bottom edge of the apron to accommodate the spikes.

Penetration Flashing

Plumbing vent pipes that extend through the roof come with metal flashing or rubber boot-type flashing to seal the penetrations. Replace all rubber boots and replace metal penetration flashing unless it is in like-new condition.

Valley Flashing

The valleys where two roof planes intersect take the brunt of water flow and will benefit from new flashing and additional precautions. The best method for sealing valleys is to install a strip of roofing felt or a waterproof membrane in the valley over the roof deck before installing roofing felt. Install galvanized metal flashing over the roofing felt, and shingle on top of that. A special technique of “lacing” the shingles in the valley is also necessary.

Vertical Wall Flashing

Anyplace where the roof plane meets a vertical wall, such as a dormer, a chimney or a split-level roof, flashing is necessary. It’s not always possible to remove the old flashing in these spots, especially if the vertical wall is brick and the original flashing was grouted into the joints. New flashing is still necessary, however, and old flashing can be cut away with aviation snips or removed after prying up clapboard siding.

Considerations

Installing new flashing is a straightforward process on roof edges, but counter flashing or step-type flashing techniques are necessary around vents and vertical walls. Since flashing covers penetrations in the roof, it pays to have a knowledgeable roofer flash these areas. Installing new flashing along brick walls is tricky and might require cutting grooves with a masonry saw to attach new flashing pieces.

About the Author

Glenda Taylor is a contractor and a full-time writer specializing in construction writing. She also enjoys writing business and finance, food and drink and pet-related articles. Her education includes marketing and a bachelor's degree in journalism from the University of Kansas.